Sync kit docs

apps/svelte.dev/content/docs/kit/30-advanced/25-errors.md

@@ -101,6 +101,54 @@ By default, unexpected errors are printed to the console (or, in production, you
 
 Unexpected errors will go through the [`handleError`](hooks#Shared-hooks-handleError) hook, where you can add your own error handling — for example, sending errors to a reporting service, or returning a custom error object which becomes `page.error`.
 
+## Rendering errors
+
+Ordinarily, if an error happens during server-side rendering (for example inside a component's `<script>` block or template), SvelteKit will return a 500 error page.
+
+Since SvelteKit 2.54 and Svelte 5.53, you can change this by enabling the experimental `handleRenderingErrors` option in your config:
+
+```js
+/// file: svelte.config.js
+/** @type {import('@sveltejs/kit').Config} */
+const config = {
+	kit: {
+		experimental: {
+			handleRenderingErrors: true
+		}
+	}
+};
+
+export default config;
+```
+
+When this is enabled, SvelteKit will wrap your route components in an error boundary. If an error occurs during rendering, the nearest [`+error.svelte`](routing#error) page will be shown, just as if the error had occurred in a `load` function.
+
+The error is first passed to [`handleError`](hooks#Shared-hooks-handleError), allowing you to report it and transform it, before the resulting object is passed to the `+error.svelte` component.
+
+> [!NOTE]
+> Since rendering errors occur after the page has started rendering, and multiple boundaries could in parallel catch distinct errors, the [`page`]($app-state#page) object (and its `error` property) will not be updated. Instead, the error is passed directly to the `+error.svelte` component as a prop.
+
+```svelte
+<!--- file: +error.svelte --->
+<script>
+	let { error } = $props();
+</script>
+
+<h1>{error.message}</h1>
+```
+
+The same applies for other error boundaries you define in your code:
+
+```svelte
+<svelte:boundary>
+	...
+	{#snippet failed(error: App.Error)}
+		<!-- error went through handleError and is of type App.Error -->
+		{error.message}
+	{/snippet}
+</svelte:boundary>
+```
+
 ## Responses
 
 If an error occurs inside `handle` or inside a [`+server.js`](routing#server) request handler, SvelteKit will respond with either a fallback error page or a JSON representation of the error object, depending on the request's `Accept` headers.

apps/svelte.dev/content/docs/kit/98-reference/50-configuration.md

@@ -513,6 +513,28 @@ forkPreloads?: boolean;
 
 Whether to enable the experimental forked preloading feature using Svelte's fork API.
 
+</div>
+</div>
+<div class="ts-block-property">
+
+```ts
+// @noErrors
+handleRenderingErrors?: boolean;
+```
+
+<div class="ts-block-property-details">
+
+<div class="ts-block-property-bullets">
+
+- <span class="tag">default</span> `false`
+
+</div>
+
+Whether to enable the experimental handling of rendering errors.
+When enabled, `<svelte:boundary>` is used to wrap components at each level
+where there's an `+error.svelte`, rendering the error page if the component fails.
+In addition, error boundaries also work on the server and the error object goes through `handleError`.
+
 </div>
 </div>